Re: Serial com with USB485 - ModBUS

No problem to connect the hardware. Connect the TX+ and RX+ from one side to the RS-485+ on the other side. Same for the -. Also connect the 0V. Some say this is not necessary but believe me it is better to connect it. btw. this is not the shielding. Shielding should be connected to the ground (earth / case).

Your master device should support this. The receiver must be disabled during transmit. Otherwise you receive your transmitted message back.

Re: Serial com with USB485 - ModBUS

First the addresses. The manual says register holding address 43756. The 4 at the start indicates that these are holding registers. Readable with ModBus command 4 and they use command 3. In practice both the same.

Try both addresses 43756 (0xAAEC) and 3756 (0x0EAC) to be sure.

The data for this register is Int32. So that is 4 bytes. On page B-6 of the manual the byte order is explained.

I think the complete command is: 01 06 0E AC 00 01 00 00 71 1A

Can you try this ?

No, I don't work at NI. 'They' will not give you these answers Sorry guys.....

Here I work. Support engineer for this half my time and repair engineer for the high-end T&M.